Low pass filters and high pass filters can be used for rejecting harmonics in communication signals. Low pass filters and high pass filters can also be used in carrier aggregation systems that combine multiple component carriers to achieve high data transmission rates in wireless communications. In carrier aggregation applications, however, low pass filters and high pass filters specify very low levels of insertion loss, which are very difficult to achieve for conventional technologies (e.g., low temperature co-fired ceramic devices). Insertion loss is a metric, usually measured in decibels (dB), that expresses the loss of signal power resulting from the insertion of a device (e.g., a low pass filter or a high pass filter) into a transmission system (e.g., a wireless network). The lower the insertion loss, the more stable and powerful the device is in efficiently propagating signals through a network.
The filter fabrication process may be compatible with standard semiconductor manufacturing processes (e.g., processes for fabricating voltage-controlled capacitors (varactors), switched-array capacitors, or other like capacitors). It may be beneficial to fabricate the components of the filter on a single substrate. Fabrication on a single substrate may also enable the creation of filters having a number of adjustable parameters due to process variables.
Fabricating high performance filters with low insertion loss is a challenge. Furthermore, reducing the electromagnetic coupling between the various components in a filter design, while decreasing the size of the filter, is also a challenge. A filter design that achieves low insertion loss, while being fabricated in an efficient and economical manner would be beneficial.